Swimming microorganisms can influence the diffusion of passive particles. The effect of this swimmer-particle interaction depends on different properties, such as the hydrodynamic field of the swimmer and the relative sizes of microorganisms and particles. We investigated an enhancement of the diffusion of silica doublets in a suspension of microalgae Chlamydomonas reinhardtii in a flat capillary. Depending on the concentration of microswimmers, the translational and rotational diffusion constants increase by several orders of magnitude in the presence of the swimming algae. For low concentrations of algae, the doublets exhibit Brownian motion in a fluctuating flow field generated by multiple swimmers. One can observe strong, diffusive transport caused by occasional large displacements. At high swimmer concentration, the algae form dense clusters, where the rotational motion of the doublets shows a subdiffusive behaviour while the translational motion remains diffusive.

中文翻译：

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活动藻类活性胶体悬浮液中细长颗粒的扩散动力学

游泳微生物会影响被动粒子的扩散。这种游泳者-粒子相互作用的效果取决于不同的特性，例如游泳者的流体动力学场以及微生物和粒子的相对大小。我们研究了在扁平毛细管中微藻莱茵衣藻悬浮液中二氧化硅双峰扩散的增强。根据微型游泳者的浓度，在游泳藻类存在的情况下，平移和旋转扩散常数会增加几个数量级。对于低浓度的藻类，双联体在多个游泳者产生的波动流场中表现出布朗运动。人们可以观察到由偶尔的大位移引起的强烈的、扩散的传输。在高游泳者浓度下，藻类形成密集的簇，